1. Field of the Invention
The invention relates in general to a phase-difference detecting apparatus, and more particularly to a phase-difference detecting apparatus, which detects phase difference between several targeted signals by delaying the phase of a detection signal.
2. Description of the Related Art
Referring to FIGS. 1A and 1B, a block diagram of a conventional phase-difference detecting apparatus and a timing diagram of relevant signals of the phase-difference detecting apparatus of FIG. 1A are respectively shown. To obtain phase difference between the timing signals CK1 and CK2 with the same frequency and different phases, the timing signals CK1 and CK2 are inputted to an exclusive or (XOR) gate to obtain an exclusive signal XS and the exclusive signal XS and a sample signal SS generated by the signal generator 130 are inputted to a flip-flop 120 to sample the exclusive signal XS by the sample signal SS and obtain a sample result SO. Afterwards, how many periods of the sample signal SS are included in the time when the sample result SO has a high signal level is counted to obtain a delay time TD corresponding to the phase difference between the timing signals CK2 and CK1. Then, the phase difference between the timing signals CK1 and CK2 can be obtained according to the delay time Td and the period of the timing signal CK1. However, the conventional phase-difference detecting apparatus 100 has several disadvantages.
In order to precisely detect the phase difference between the timing signals CK1 and CK2 via the conventional phase-difference detecting apparatus 100, the frequency of the sample signal SS should be very much higher than the frequency of the timing signals CK1 and CK2, such as by more than 20 times. However, in a normal electronic apparatus, most of the timing signals have a frequency close to the maximum frequency permitted in the circuit hardware condition. Therefore, in a normal practical application, the phase difference between the timing signals CK1 and CK2 can be only measured by using a measuring signal SS with a frequency slightly higher than those of the timing signals, which results in lower precision of the measurement result. Besides, to generate the measuring signal SS with a frequency higher than those of the timing signals CK1 and CK2 requires an expensive timing-signal generator 130, which in turn increases the cost of the phase-difference detecting apparatus 100.